Behavioral Effects of Ulva lactuca Extract in an Ovalbumin-induced Hypersensitivity Dermatitis Rat Model

The purpose of this study was to investigate the effects of Ulva lactuca (sea lettuce) extracts on changes in behavior indicative of depression-like behavior, memory impairment, and hyperalgesia in a rat model of ovalbumin-induced hypersensitivity dermatitis.Experimental groups were equivalent to control group, vehicle group, Ulva lactuca (low dose) group, Ulva lactuca (high dose) group, and placebo (Allegra) group.The oral treatment was performed during 4 weeks.Behavioral tests were conducted (tail suspension test [TST], swimming test [ST], Y-maze, and the tail-flick test).Compared with vehicle treatment, a significant aggravation was observed in the vehicle-treated group in terms of neuropsychiatric measures, such as depressive and lethargic behavior (immobility time, +76%-86%), in addition to cognitive impairment anxiety (spontaneous alternation rate, 32% ± 4%), and enhanced pain sensitivity (response time, 12.5 ± 2.1 seconds).In contrast, Ulva lactuca extract treatment, particularly at high doses, resulted in significantly beneficial effects in the TST, ST, Y-maze, and tail-flick response assay, suppressing immobility time by 47%-58% (P < 0.01) in the TST and ST, increasing the alternation rate to 51% ± 6% (P < 0.01) in the Y-maze, and prolonging the tail-flick response time to 18.3 ± 3.4 seconds (P < 0.05), similar to those of the positive control group.These results suggest that an extract of Ulva lactuca could be a safe candidate in natural therapies for the treatment of neuropathic pain complications and pain sensitization, including neuropathic pain, related to hypersensitivity dermatitis through the skin-brain axis.